Decopperizing lead with phosphorus



Patented Apr. 27, 1937 PATENT OFFICE DECOPPERIZING LEAD WITH PHOS-PHORUS Jesse 0. Better-ton and Yurii E. Lebedefi, Me-

tuchen, N. J., assignors to American Smelting and Refining Company, NewYork, N. Y., a corporation of New Jersey No Drawing. Application March2, 1935,

. Serial No. 9,106

8 Claims.

This invention relates to the metallurgy of lead and has for its objectthe provision of certain improvements in removing copper from lead.

The invention provides a process for decopperizing lead (includingcertain alloys thereof) which is of particular importance in treatinglead containing copper in the relatively small amounts such as oftenpersist or remain in the metal after many of the usual metallurgicalproc- 10 esses to which lead is ordinarily subjected.

In accordance with the invention, the copperbearing lead is melted, andphosphorus, either in elemental or appropriate alloy form, is thoroughlyincorporated in the molten bath. As a result the copper in the moltenbath combines with the phosphorus present to form a dross and as such iseliminated from the metal. The formation of the copper phosphide drossand its separation from the resulting decopperized metal may befacilitated by liquation of the bath to its freezing point. As will beapparent from the. specific examples hereinafter set forth, a virtuallycomplete elimination of copper may be readily affected by the presentprocess.

As above indicated, the phosphorus may be added either in elemental orsuitable alloy form. Also, it may be incorporated in the bath in avariety of manners, as, for example, by addition to the vortex createdby the action of an ordinary mixing machine, by submergence in a basketin the bath through which the metal is circulated, etc. Thoroughincorporation of the phosphorus in the metal is readily insured bystirring.

Naturally the amount of phosphorus or phosphorus alloy (of knowncomposition) used will depend upon the copper content of the metal andthe degree of separation desired, the normal operation being to supplythat amount of phosphorus or phosphorus-yielding material whichissuflicient to combine with the copper content of the metal. Any residualor excess phosphorus, that is, phosphorus remaining in the metal afterelimination of the copper, may be readily removed by means of niter orother oxidizing agents, or by any other suitable procedure.

For the purpose of more fully illustrating the improved process of theinvention, the following typical examples of the process as applied tothe treatment of copper-bearing lead and antimonial lead are given:

' Example 1 In this instance, 141.1 parts byweight of copper-bearingantimonial lead were melted in a suitable kettle provided with a mixerand melting dross amounting to 1.3 parts by weight was skimmed. To theremaining bath (139.8 parts by weight) which analyzed 6.31% antimony and0.091% copper, 0.263 part by weight of phosphorus was added via thevortex created by the mixer with which the bath was continuouslystirred. The bath was maintained within a temperature range of 650 F. to720 F. throughout the period in which the phosphorus was added. Thisperiod was forty minutes, following which the mixing was continued forfive additional minutes to insure complete incorporation of thephosphorus in the antimonial lead bath and to permit the reactionbetween the phosphorus and copper to run to completion.

The dross which formed was removed from the kettle at a temperature of650 F. and amounted to 15.5 parts by weight with a copper content of0.82%. The bath (124.5 parts by weight) contained 6.05% antimony and wasfound by spectro graphic analysis to be entirely free from copper.

Example 2 One hundred fifty two parts by weight of copper-bearingrefined lead were melted in a suitable kettle and melting drossamounting to 1.9 parts by weight was skimmed, leaving a bath comprising160.1 parts by weight which analyzed 0.081% copper.

Five parts by weight of phosphor-tin alloy containing 2.61% phosphoruswere added to the bath at a temperature of 650 F. and allowed to meltand the entire charge was then stirred for ten minutes. The resultingdross, which was removed at a temperature of 650 F. and which analyzed1.03% copper was of a very crystalline metallic nature and readilyamenable to pressing.

The residual bath comprised 143.3 parts by weight and contained onlyspectroscopic traces of copper, less than 0.0001%.

Example 3 Apart from some details of operation, this example Wassubstantially a repetition of the preceding one, except for the use ofphosphorus in elemental instead of alloy form.

In this instance 154.3 parts by weight of copper-bearing refined leadwere melted and 1.7 parts by weight of melting dross skimmed from thekettle. The bath then comprised 152.6 parts by weight and analyzed0.081% copper.

The bath was stirred and 0.130 parts by weight of free phosphorus addedto the vortex of the mixer, the operation consuming a period of twentyminutes and the bath being maintained r within a temperature range of650 F. to 670 F.

Stirring of the bath was continued for ten minutes at the sametemperature following the addition of the last of the phosphorus.

The dross of a crystalline and metallic nature as above and whichamounted to 9.75 parts by weight was skimmed at 650 F. The lead bathamounting to 142.9 parts by weight was analyzed and found to containonly 0.001% copper.

Following the removal of the dross, the bath was reheated to 750 F. and0.1 part by weight of free phosphorus was added within a period offifteen minutes. The stirring was continued for four additional minutesand the dross,

amounting to 2.5 parts by weight, skimmed.

Upon examination the final lead which amounted to 140.4 parts-by weightwas found to be spectroscopically copper free.

It will thus be appreciated that the present invention provides a.direct, eflicient and clean out process for removing copper from leadand certain alloys thereof.

It has further been found that the lead prodnot itself exhibits certainimproved properties which it is believed are probably due to thepresence of minute quantities of phosphorus, distributed throughout thefinal product. For example, the metal remains bright and does nottarnish for an indefinite period of time. tion, it is of exceptionallyhigh quality as to appearance, softness and other characteristics.

While various specific disclosures have been made in order to fullyillustrate and explain the invention, it will readily be appreciated bythose skilled in the art that various changes and modifications areembraced within the scope of the invention and may be employed inadapting it to varying situations, conditions and uses.

What is claimed is:

1. The process for removing copper from lead which comprisesestablishing a molten bath of the metal, incorporating aphosphorus-yielding substance therein, cooling said bath and separatingthe dross therefrom.

2. The process for treating lead and antimoniallead containing copperwhich comprises reacting a molten bath of the metal with phosphorus andseparating the resulting dross in which copper is concentrated from themetal.

In addi- 3. The process for treating ,copperrbearing lead whichcomprises establishing a' molten bath thereof having a temperature notmaterially exceeding 750 F., incorporating suflicient phosphorus thereinto insure complete reaction with the copper, cooling the bath toapproximately its freezing point and separating the dross from thedecopperized lead.

- 4. The process for removing copper from copper-bearing lead whichcomprises treating-the lead while molten with phosphorus in quantitiessuiiicient to completely convert the copper in the lead intophosphor-copper, and separating the resulting phosphor-copper from theremaining lead.

5. The process for removing copper from copper-bearing lead whichcomprises preparing a molten bath of the lead, mixing thereinphosphor-tin alloy containing a known amount of phosphorus and inquantities sufiicient to react with the amount of copper in the lead,and separating the resulting phosphor-copper dross from the lead.

6. The process for removing copper from. copper-bearing antimonial leadwhich comprises mixing with a molten bath of the said metal suficientphosphor-tin of known composition to reaction to proceed and separatingthe resultingphosphor-copper reaction products from the metal of thebath.

7. The process for decopperizing lead which comprises melting a bath oflead containing predetermined amounts of copper, adding to the bath anamount of phorphorus in reactive form sufiicient to combine with thecopper while maintaining the bath 'at a temperature range ofapproximately 650 F.'to approximately 720 F'., and separating theresulting copper-containing dross.

8. The process for treating lead contaminated with copper whichcomprises forming a molten bath thereof, incorporating in the bathsufilcient phosphorus in available form to combine with all of thecopper in the bath and impart thereto a small residual phosphoruscontent and sep-, arating the resulting dross and decopperized lead.

JESSE O. BETTERTON. YURII E. LEBEDEFF,

